The relative importance and the mechanism by which prostaglandins regulate renin secretion is under study. The techniques used are the superfusion of the rat renal cortical slice and urinary prostaglandins as a measure of real prostaglandin production. We are studying the interaction of prostaglandins with other stimuli of renin secretion, and are using inhibitors of the various prostaglandin pathways to determine which prostaglandin is the most important in the regulation of renin secretion. Since only in the female does urinary excretion of PGE2 reflect renal prostaglandin production, we will continue to measure urinary PGE excretion in female patients with various forms of hypertension and renal disease and will assess the effect of non-sterodial anti-inflammatory drugs on urinary PGE excretion and renal function.